1. Field of the Invention
The present invention relates to liquid crystal compounds and liquid crystal compositions containing the same.
2. Description of the Background
Display modes of liquid crystal display elements now widely in use are those of the twist nematic type (TN type) and dynamic scattering type (DS type). These modes are display modes with nematic liquid crystal cells containing nematic liquid crystals as a main component. The conventional nematic liquid crystal cells are disadvantageous in that the response speed is so slow that a response speed only of the order of several m sec is obtained at most. This drawback greatly narrows the applicable range of nematic crystal cells. However, it has recently been recognized that by using smectic liquid cells, higher response speeds are possible.
Some optically active smectic liquid crystals are known to exhibit a strong dielectric property. Examples of liquid crystals exhibiting a strong dielectric property, are representative compounds such as 4-(4-n-decyloxybenzylideneamino) cinnamic acid-2-methyl butyl ester (hereinafter abridged as DOBAMBC) as synthesized by R. B. Meyer et al. in 1975. These compounds are characterized by exhibiting a strong dielectric property in the chiral smectic C phase (J. Physique, 36, L-69 (1975).
Recently, a high speed response of .mu. sec order has been found in a thin film cell of DOBAMBC by N. A. Clark et al. (Appl. Phys. Lett. 36, 89 (1980)). Thereafter, strongly dielectric liquid crystals have been studied due to their high speed response as a material usable not only for displays such as liquid crystal televisions but also as a raw material for optoelectronics and related devices such as light printer heads, optical Fourier transform devices and light values.
Display devices using strongly dielectric liquid crystals can produce printing with short pulses, thus making memorization thereof possible, and thus also making it possible to easily produce large areas of display.
Unfortunately, display devices using a strongly dielectric crystal composition are not yet practicable due to the fact that the response speed of the composition is inadequate and the usable temperature range is prohibitively narrow. Thus, a need continues to exist for a strongly dielectric liquid crystal composition which has a high response speed over a wide range of temperature.